1. Field of the Invention
The present invention relates to a TS data filtering circuit in a digital broadcasting receiver for receiving digital broadcasting such as BS digital broadcasting.
2. Description of the Prior Art
In a BS digital broadcasting receiver, matching judgment in a case where data in a necessary TS packet are separated from an MPEG transport stream (TS) is made only by hardware, as shown in FIG. 2. Therefore, a range in which the matching judgment is made is limited to a previously determined range W of several bytes previously determined from the head of each of TS packets.
In the future, it is considered that identification data is inserted into a position beyond the range W from the head of the TS packet. In such a case, it is considered that matching judgment on data, beyond the range W, in a data row in the TS packet is made by software.
Consider a case where the range in which the matching judgment by hardware is made is a range of 16 bytes from the head of the TS packet, for example. In this case, when identification data relating to matching judgment is inserted into a position corresponding to the 32-th byte from the head of a TS packet {circle around (1)} shown in FIG. 2, the following operations are performed.
Specifically, the matching judgment by hardware is made in a range of 16 bytes from the head of the TS packet {circle around (1)}. At this stage, when it cannot be judged whether or not the data row is a data row to be acquired, the whole of the data row in the TS packet {circle around (1)} is stored once in a memory by a TS data separation portion, and the matching judgment by software is then made on data, corresponding to the 17-th byte and the subsequent bytes from the head of the TS packet {circle around (1)}, in the data row stored in the memory.
When it is not judged that the data row in the TS packet {circle around (1)} is a data row to be acquired at the position corresponding to the 32-th byte from the head of the TS packet {circle around (1)}, the TS data separation portion is restarted.
In such a method, when a data row in a TS packet {circle around (2)} shown in FIG. 2 is a data row to be acquired, for example, the matching judgment by software is made after the whole of the data row in the TS packet {circle around (1)} is stored in the memory. Accordingly, it takes long until the TS data separation portion is restarted, so that the data row in the TS packet {circle around (2)} cannot be judged.
An object of the present invention is to provide a TS data filtering circuit in a digital broadcasting receiver, wherein in a case where identification data required to judge whether or not data is to be acquired is inserted into a position beyond a range in which matching judgment by hardware is made from the head of a TS packet, time required for the matching judgment on the TS packet can be shortened, thereby avoiding the possibility that a data row to be acquired cannot be judged.
A TS data filtering circuit according to the present invention is characterized by comprising a matching judgment portion for making matching judgment on data included in a predetermined range from the head of a TS packet by hardware; storage means for storing, when it cannot be judged whether or not a data row in the TS packet is a data row to be acquired by the matching judgment in the matching judgement portion, data in the TS packet in a memory; matching judgment means for making matching judgment by software on the data stored in the memory by the storage means; and means for starting the matching judgment in the matching judgment means at a stage where data corresponding to the number of effective bytes previously determined are stored in the memory in the process of storing the data in the memory by the storage means.
When the matching judgment means does not judge that the data row is a data row to be acquired, matching judgment on the subsequent TS packet is started by the matching judgment portion.